The present invention relates generally to the field of electrosurgery, and, more particularly, to high efficiency surgical devices and methods which use of high frequency (RF) electrical power for cutting, bulk removal by vaporization with externally supplied conductive liquid irrigants.
The present invention provides a system and method for performing electrosurgical cutting, ablation (volumetric tissue vaporization), coagulation or modification within or on the surface of a patient. The system and method of the invention herein disclosed may be used in relatively dry environments, for instance, for oral, otolaryngological, laparoscopic, and dermatologic procedures.
Electrosurgical procedures require a proper electrosurgical generator, which supplies the Radio Frequency (RF) electrical power, and a proper surgical electrode (also known as an electrosurgical probe). Under appropriate conditions the desired surgical effects are accomplished.
Note: in common terminology and as used herein the term “electrode” may refer to one or more components of an electrosurgical device (such as an active electrode or a return electrode) or to the entire device, as in an “ablator electrode”. Electrosurgical devices may also be referred to as “probes”.
An electrosurgical probe, in general, is composed of a metallic conductor surrounded by a dielectric insulator (for example plastic, ceramic or glass) except for the exposed metallic electrode. The probe electrode is often immersed in a conducting fluid, either filling a natural or created cavity or applied as irrigant to a “dry” site, and is brought in contact with or close proximity to the tissue structure during the electrosurgical procedure. The probe is energized, typically at a voltage of few hundred to a few thousand volts, using an RF generator operating at a frequency between 100 kHz to over 4 MHz. This voltage induces a current in the conductive liquid and nearby tissue. This current heats the liquid and tissue, the most intense heating occurring in the region very close to the electrode where the current density is highest. At points where the current density is sufficiently high, the liquid boils locally and many steam bubbles are created, the steam bubbles eventually insulating part or all of the electrode. Electrical breakdown in the form of an arc (spark) occurs in the bubbles which insulate the electrode. The sparks in these bubbles are channels of high temperature ionized gas, or plasma (temperature of about a few thousand degrees Kelvin). These high current density sparks, heat, vaporize (ablate) or cut the tissue (depending on the specific surgical procedure and the probe geometry) that is in contact with the spark or the adjacent heated fluid.
Many surgical procedures are not performed inside a natural or formed body cavity and as such are not performed on structures submerged under a conductive liquid. In laparoscopic procedures, for instance, the abdominal cavity is pressurized with carbon dioxide to provide working space for the instruments and to improve the surgeon's visibility of the surgical site. Other procedures, such as oral surgery, the ablation and necrosis of diseased tissue, or the ablation of epidermal tissue, are also typically performed in an environment in which the target tissue is not submerged. In such cases it is necessary to provide a conductive irrigant to the region surrounding the active electrode(s), and frequently also to aspirate debris and liquid from the site. Such irrigant may be applied by a means external to the instrument; however, having an irrigation means internal or attached to the instrument generally provides better control and placement. This is also true for aspiration of fluid and debris. External means may be used for aspiration from the site; however, aspiration through the instrument distal end provides improved fluid control and may, in some cases, draw tissue toward the active electrode thereby enhancing performance.
Electrosurgical devices having a means for irrigating a site, and/or means for aspirating fluid, bubbles and debris from a site are well known. Smith in U.S. Pat. No. 5,195,959 teaches an electrosurgical device with suction and irrigation. Bales, et al in U.S. Pat. No. 4,682,596 teach a catheter for electrosurgical removal of plaque buildup in blood vessels, the catheter having lumens for supplying irrigant to the region of the instrument distal tip and for aspirating debris from the region. Hagen in U.S. Pat. No. 5,277,696 teaches a high frequency coagulation instrument with means for irrigation and aspiration from the region of the instrument tip. Pao in U.S. Pat. No. 4,674,499 teaches a coaxial bipolar probe with suction and/or irrigation. Eggers in U.S. Pat. No. 6,066,134 teaches a method for electrosurgical cutting and coagulation which uses a bipolar probe having means for irrigating and aspirating from the region of the probe distal tip. The Eggers device uses the irrigant flow to provide a return path to a return electrode recessed axially a distance away from the active electrode(s).
One application of electrosurgical technique is the removal of a portion of tissue from a vascular surrounding tissue bed in a “dry” environment, that is, in an environment in which conductive irrigant is supplied to the surgical site. Such removal requires the effective vaporization of connecting tissue to allow removal of the tissue portion, and also coagulation of the adjacent remaining tissue to prevent bleeding. Debris and irrigant are removed from the site by aspiration, either by a means external to the electrosurgical instrument or through external means.
It is accordingly an object of this invention to produce an electrosurgical probe which is able to effect the removal of a tissue portion from a surrounding vascular bed while minimizing bleeding.
It is also an object of this invention to produce an electrosurgical probe which has a simple structure so that it is producible at low cost.
It is additionally an object of this invention to produce an electrosurgical probe in which tissue may be either vaporized or coagulated through selection of the probe surface in contact with the tissue.